Protocol M98-888 is a Phase III, open-label, randomized, positive controlled, multi-center, multi-country study comparing two regimens. Approximately 300 subject who have HIV RNA levels of at least 1,000 copies/ml and at most 100,000 copies/ml (Roche Amlicor) while treated with the regimen consisting of a single protease inhibitors and two NRTIs that has not been changed for a least twelve weeks will be randomized in this study. Subject will be equally randomized to either the Investigator Selected Protease Inhibitors(s) or ABT-378/ritoanvir in regimen.